A new patch has been released for Diablo III that primarily enables the Real Money Auction House, which is now open in the Americas. The patch also removes "Error 37", though only by dropping players back to the login automatically if the authenticators are busy as I understand it.
The RMAH is the big news and a new blog entry describes the service, currencies available and the security measures in place:

Quote:

The Diablo® III real-money auction house is now available in the Americas game region for the U.S. dollar, Australian dollar, and Mexican peso. With the real-money auction house, players will be able to buy and sell the loot they find in the game using actual currency via approved third-party payment services or using their Battle.net® Balance.
The real-money auction house for the Europe game region and the remaining Americas game region currencies (Chilean peso, Argentine peso, and Brazilian real) will launch in the near future. We are rolling out elements of the real-money auction house separately to ensure all of our players have the smoothest possible experience. We'll have more information on the availability of the European real-money auction house and the remaining Americas currencies soon.

Not sure how effective this AH will be. I've found in both regular and hardcore mode, that because so many people dump stuff on the AHs, all I have to do is use 'gold find' equipment and then just buy all the best gear with exactly the stats I want for a few thousand gold each. It's far better than bothering with magic find.